Action News has learned that Sandusky, a former assistant football coach at Penn State University, is under federal investigation.
UPDATE: ABC News: Sandusky sent "creepy" love letters
Sources tell Action News the investigation centers around Victim 4 in the state's case. Federal investigators are probing Sandusky for allegedly taking the child across state lines to engage in sex.
Interact: The latest tweets and updates from Chad Pradelli
According to the Grand Jury report released by the Pennsylvania Attorney General's office in November of last year, Victim 4 is now 28 years old and was a participant in the Sandusky-founded charity "The Second Mile."
Victim 4 testified before a grand jury that Sandusky showered him with gifts and the victim accompanied Sandusky to the 1998 Outback Bowl in Tampa and the 1999 Alamo Bowl in San Antonio.
The victim, who was then a young teen, testified Sandusky threatened to send him home when the victim resisted the then defensive coordinators advances.
Action News spoke with Ben Andreozzi, the civil attorney representing Victim 4.
"My understanding or my thought is it possibly would come to fruition after these state charges are considered and ruled on by the jury," Andreozzi said.
Andreozzi was unaware of the target letter sent to Sandusky's attorneys.
A target is a person whom the prosecutor or grand jury has substantial evidence linking him or her to the commission of a crime.
The letter means the feds believe they have substantial evidence and an indictment is likely.
Andreozzi expects his client to be the first on the stand when the state trial begins next week
"I think it's fair to say he's extremely anxious to get this over with; this has been the most difficult time of his life," Andreozzi said.
In the state's case of sexual abuse, jury selection begins tomorrow and the trial is expected to begin next week.
Sandusky's attorney Joe Amendola declined to comment to Action News citing the gag order in the Sandusky case. Pa. Attorney General spokesman Nils Frederiksen also declined comment to Action News citing the gag order, as well.
Sandusky, 68, faces 52 charges he abused 10 boys over 15 years, allegations he has repeatedly denied. He remains confined to his home.
Alleged victims of Sandusky will have to testify using their real names, the judge ruled Monday.
"We're really disappointed in this decision and concerned on its impact on the victims' in this particular case and also for victims across Pennsylvania who are contemplating whether or not to report their own assault," Kristen Houser, Vice President of Communications and Development with the Pennsylvania Coaltion Against Rape, said.
The judged also ruled tweets or other electronic communications by reporters will not be permitted during the trial.
Meanwhile, Sandusky's hopes for a last-minute delay in his state trial were dashed when the state Supreme Court issued a one-paragraph order that denied a sealed motion but did not disclose the justices' reasoning.
For more on the trial, click here.
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The Associated Press contributed to this report.
